1. Field of the Invention
The present invention generally relates to laser diode modules and, more particularly, to a laser diode module suitably applied to a bar code reader in which a laser diode is used as a light source.
2. Description of the Prior Art
Various types of laser sources have been proposed. In the past, a He--Ne laser was widely used. Recently, semiconductor laser diodes have been proposed and applied to various fields as light sources. Such semiconductor laser diodes contribute to down-sizing of various devices.
A bar code reader that optically reads a bar code uses a semiconductor laser diode (hereinafter, simply referred to as a laser diode). Normally, a laser diode is combined with optical elements such as lenses, and a laser diode module made up of the laser diode and the optical elements is provided as a light source. A light emitted from the laser diode is optically processed by the optical elements of the laser diode module and is projected onto a bar code via an optical scanning system outside of the laser diode module.
The performance of the bar code reader greatly depends on the performance of the laser diode module. Conventionally, a complex adjustment mechanism is employed in the laser diode module in order to improve the performance thereof. For example, such an adjustment mechanism is designed to adjust the positions of optical elements, such as lenses. By way of another example, a plurality of optical elements are used to improve the performance of the laser diode module.
From the above viewpoints, it is required to provide a simple laser diode module capable of providing good performance by a simple adjustment mechanism.